Note: Descriptions are shown in the official language in which they were submitted.
~2~
APPARATUS FOR ~EGULATING AIR FLOW THROt~GH
AN AIR PORT OF A CHEMICAL RECOVERY EtlRNACE
Back round of the Invention
The present invention relates to furnaces and
particularly to improved apparatus ~Eor regulating
air flow through a port introducing co~bustion air
into the firebox of a furnace and including appara-
tus for automatically cleaning the air port.
Wood pulp for papermaking is usually manufac-
tured according to the sulfate process wherein wood
chips are treated with a cooking liquor including
sodium sulfide and sodium hydroxide. The wood
chips and the cooking liquor, called "white
liquor," are cooked in a digester under predeter--
mined heat and temperature conditions. After
cooking, the used liquor, termed "black liquor,"
containing spent cooking chemicals and soluble
residue from the cook, is washed out of the pulp
and treated in a recovery unit where the cooking
chemicals are reclaimed. Without reclamation and
reuse of the cooking chemicals, the cost of the
papermaking process would be prohibitive~
In the recovery process, the black liquor is
first concentrated by evaporation to a water solu-
tion containing about 65 percent solids, which
solution is then sprayed into the firebox of a
black liquor recovery boiler, a type of chemical
reduction furnace. The chemical reduction furnace
is a reactor wherein the processes of evaporation,
gasification, pyrolysis, oxidation and reduction
all occur interdependently during recovery-of the
cooking chemicals. The orqanic materials in the
black liquor, lignin and other wood extracts, main-
tain combustion in the firebox, and the heat pro-
2 ~2~ 9
duced dries and melts the spent cooking chemicals
as they fall to the floor of the firebox, where
they build a mound of material called a char bed.
The char bed is further heated to further liquefy
the chemicals into a molten s~elt tha~ flows out of
the furnace through a smelt spout to a collection
tank. Concurrently, combustion heat is employed to
generate steam in a water wall of the boiler for
use as process steam and for generating electricity.
The combustion process requires the introduc-
tion of large volumes of air into the firebox, air
comprising about 80 percent of the ~aterial
entering the furnace. The combustion air is dis-
tributed~by means of wind boxes or ducts disposed
at several levels in surrounding relation to the
firebox and outside the walls of the furnace. The
air is forced into the firebox from the wind boxes
through a plurality of passages or air ports in the
walls of the furnace, viz.: primary, secondary and
tertiary air ports. The primary air ports, through
which about 40 to 50 percent of the air enters the
furnace, are disposed on the side walls of the
firebox near the bottom of the furnace and close to
the char bed. The air supplied to the primary air
ports is at a comparatively low pressure in order
to promote a reducing atmosphere in the burning
mass of char. The secondary air ports, which are
fewer in number than the primary air ports and
through which about 35 percent of the air enters
the furnace, are disposed around the walls of the
firebox, higher than the primary air ports, and
usually beIow the level of the entry conduits
through which the black liquor is sprayed into the
firebox. Air sup~lied through the secondary air
ports is at a slightly higher pressure in order to
.
3 ~2~
promote burning of combustible gasses rising from
the glowi~ng mass of the char bed. While the pri-
mary air ports provide a relatively large volume of
air with considerable turbulence for maintaining a
fireball in the char bed, the secondary air ports
are intended to provide a finer control and distri-
bution of air above the char bed and distribute the
air evenly in the black liquor spray to support the
combustion thereof. ~ir is supplied through the
tertiary air ports at a still higher pressure to
promote combustion of gases rising through the
firebox, the tertiary air ports being higher on the
wall of the furnace than the secondary air ports.
The black liquor sprayed into the firebox,
having a consistency like warm 60 weight oil,
swirls, bur~s and falls toward the bottom of the
firebox in the form of combustion products com-
prising char material and smelt. The smelt and
char material contact and flow down the outer walls
of the firebox and, cooled by the inflowing air,
form excrescent deposits around edges of the air
ports, particularly along the top edges of the
secondary air ports where the excrescent material
builds up and outward under influence of air
rushing through the secondary air port~ Such
buildup of char material can block air flow through
a port by as much as ten percent. Therefore,
furnace operation tends to be inefficient and
unpredictable with an attendant decrease in the
amount of chemicals that can be recovered, a
decrease in the amount of steam produced per unit
of fuel, and increased emission of noxious gases
such as hydrogen sulfide, carbon mono~ide and sul-
fur dioxide. In accordance with customary prac-
tice, the char buildup is periodically removed
4 ~ 9
either by manually inserting a cleaning rod intothe air ports successively around the boiler or by
actuating mechanized cleaning apparatus mounted in
the air ports. With the passage of time, and
particularly when cleaning is effec~ed by manual
rodding of the air ports, gradual buildup of char
material intermittentl~ around the furnace can
- cause changes in the volume of combustion air, as
well as changes in air distribution~ velocity and
press~re.
The volume and distribution of combustion air
supplied to the furnace will also vary depending on
the load of the furnace and the,~oisture content of
the liquor being reduced. The distribution and
volume of air entering a furnace is conveniently
adjusted by regulating means such as dampers pro-
vided in supply conduits of the wind boxes.
Dampers may also be provided at various locations
in the wind boxes, and individual air ports may
furthermore be provided with a damper, thus making
possible a selective distribution of air within
each wind box, or in each wind-box passage or each
air port, respectively, thereby maintaining the
desired air supply in all parts of the furnace.
Separate apparatus for cleaning openings in a
recovery furnace are known. See, for example, my
U.S. patent 4,423,533 entitled FURNACE AIR PORT
CLEANER. Apparatus combining the function of air-
port cleaning and air-flow damping are also known;
however,'such dual purpose apparatus have been
found to have certain disadvantages in that either
the air damping or the cleaning is unsatisfactory.
Cleaning apparatus designed to be effective for
that purpose, when used as a damper, may be sub-
jected to excessive heat from the furnace and
~%~
deteriorate rapidly. The aforementioned copending
application discloses a cleaning head for use in
secondary air ports that may be employed also as a
damper to control the flow of combustion air
through the air port. For this purpose, the cage-
like structure of the cleaning heacl is enclosed,
and the mounting frame is partially or completely
enclosed or wa}led in, so that, for a given posi-
tion of the cleaning head, air flow tends to be
closed off. The position of the cleaning head may
be varied to accomplish cleaning or to effect a
different air flow. It has been found that a
cleaning element utilized as a damper partially or
fully blocking an air port, i.e., extending into
the air port, often is subjected to excessive heat
from the furnace, It is thus desirable to employ a
separate damper that is disposed near, bu~ spaced
apart some distance inside the wind box fro~ the
air-port opening.
On the other hand, a device designed to func-
tion effectively as a damper, when extended into
the air port for cleaning the same, often proves to
b~ ineffective for that purpose because the shape
of the damper is not conducive to cleaning the
opening. Accordingly, separate air damping and
air-port cleaning apparatus are desirable over dual
purpose devices because more uniform and stable air
flow is maintained through the air ports, resulting
in more efficient operation of the furnace.
A damper that controls the air flow to a
particular air port ordinarily is located near the
air port, and consequently may interfere with the
operati~n of separate automatic cleaning apparatus
installed in the air port. If unlimited space were
available, a damper could be installed upstream of
21~
the cleaning apparatus in the passage supplying air
to the air port; however, space adjacent to an air
port for installing such apparatus is often limited
and constructing such additional space is costly.
FurtherO when a damper is retracted or moved out of
the way of cleaning apparatus, it is often neces-
sary to ~osition the damper such that air flow
through the passage to the air port is blocked,
which is undesirable because without positive air
pressure outside the air port, effluent from the
furnace could enter the air duct and foul or damage
the mechanisms.
It is accordingly a primary object of the
present invention to provide improved apparatus for
regulating the flow of combustion air in a chemical
recovery furnace.
It is another object of the present invention
to provide improved air regulating apparatus
installable in an air port of a chemical recovery
furnace and including air-port cleaning apparat~s
that operates cooperatively with a damper mechanism
Another object of the present invention is to
provide i~proved air regulating apparatus including
air port cleaning apparatus for increasing the
operational stability of a blac~ liquor recovery
boiler.
It is a further object of the present inven-
tion to provide improved air regulating apparatus
operating in concert with air port cleaning appara-
tus for enhancing the efficiency of chemicalrecovery, increasing steam production, and reducing
sulfur dioxide and carbon monoxide emissions from a
black liquor recovery boiler.
~2~ 3
Summar of the Invention
y
According to the present invention, in a pre-
ferred embodiment thereof, a furnace air port is
provided with apparatus including an adjustable
damper and a cleaning head pivotally mounted in a
plenum adjacent to the port, the cleaning head
being adapted for automatic insert:ion into the air
port and partially inside the firebo% vertically
beyond an edge of the air port to clislodge excres-
cent material built up on the edge. Means areprovided for retracting the damper out of the way
of the cleaning head and moving the cleaning head
into the air port during a cleaning cycle and
subsequently retracting the cleaning head and repo-
sitioning the da~per after cleaning has beenaccomplished.
In another embodiment according to the present
invention, the cleaning head is constructed as a
metal frame substantially the size of the air port,
so as to sweep along all the edges of the air port
when inserted therein to dislodge excrescent
material or char buildup therefrom. The posterior
side of the frame is closed such that, in the
retracted position, the posterior surface of the
cleaning head serves as a closure of an opening in
the top of the plenum chamber, and when the
cleaning head moves away from the retracted posi-
tion during a cleaning cycle, air flows through the
opening into the air port providing a blowing
action that augments cleaning and cools the
cleaning head.
In accordance with a particular embodiment of
the invention, shield plates are provided on the
cleaning apparatus for insertion into the air port
to protect boiler tubes located inside the furnace
I
~g~
from damage due to contact by the moving cleaning
head.
The apparatus according to the present inven-
tion is easily removable from the air port. In
particular, the apparatus is affixed to a plate
which is attached to a flange on the external wall
of the wind box. For repair or servicing, the
apparatus according to the present invention is
thus easi~ly removed from the wind box.
The apparatus according to the instant inven-
tion is suitably operated at regular intervals on
an auto~atically timed basis so as to keep the air
port substantially clear of excrescent material
and without interfering with air flow damping,
which results in improved stability of furnace
operation. Consequently, more efficient recovery
of chemicals is realized, as well as an increase
in steam production and decrease in the emission
of pollutant gasses. While only a single appara-
tus according to the present invention is illus-
trated and described herein, it is understood that
a plurality of such apparatus are ordinarily dis-
posed around a particular firebox so as to clean a
comparatively large number of air inlets. The
separate apparatus can be operated either sequen-
tially or simuttaneously.
Drawings
While the invention is set forth with particu-
larity in the appended claimsl other objects,features, the organization and method of operation
of the invention will become more apparent, and the
invention will best be understood by referring to
the following detailed description in conjunction
with the accompanying drawings, in which:
~3;~
FIG. 1 is a schematic viéw of a portion of a
black liquor recovery boiler of a type with which
the present invention may be employed, and showing
one embodiment of the invention installed therein;
FIG. 2 is a side elevatio~ view, partially cut
away, of apparatus according to the instant inven-
tion, and shQwing ~he damper in a closed position
- and the cleaning head extended;
FIG. 3 is a view, partially cut away, taken
along lines 3-3 of FIG. 2;
FIG. 4 is a perspective view of a cleaniny
head used in apparatus accordin~ to the present
invention; and
FIG.~5 is a view taken along lines 5-5 of FIG.
2; and
FIGS. 6-8 show an alternative embodiment of
apparatus according to the instant invention.
Description of the Preferred Embodiment
Referring now to the various views of the
drawing for a ~ore detailed description of the
construction, function, operation and other
features of the instant invention by characters of
reference, FIG. 1 shows a black liquor recovery
boiler 10 which comprises a firebox 12 of a steam
boiler. Black liquor is sprayed through a conduit
14 into the firebox 12, where the organic materials
in the black liquor are ignited, the chemicals and
combustion products being deposited on the floor of
the firebox as a char bed 16. A first wind box 18
substantially surrounds the firebox 12 and delivers
co~bustion air under pressure into the firebox
through a plurality of primary air ports 2a formed
in the wall 22 of the firebox 12 around the peri-
phery thereof at the level of the char bed 16 to
maintain a fireball in the char bed. A molten
chemical-containing smelt 24 is recovered from the
burning char bed 16 through smelt spouts 26 dis-
posed in the bottom of the firebox 12, the smelt
being collected for further treatment.
A second wind box 28 s~bstantially surrounds
the firebox 12 and delivers combustion air under
pressure into the firebox through a plurality of
secondary air ports such as air port 30 formed in
the wall 22 of the firebox 12 around the periphery
thereof above the char bed 16 and below the level
of the black liquor entry conduit 14 for supporting
the initial combustion of the organic materials in
the black liquor. As previously described herein,
excrescent material 32 comprising hardened smelt
and char material forms on the walls 22 of the
firebox, particularly above the edges of the
secondary air ports 30, as illustrated in FIG. 1.
Referring now to FIGS. 1-4, in accordance with
the present invention, apparatus 34 for regulating
the flow of air into the air port 30 is installed
in the second wind box 28 and attached to an outer
wall 36 of the wind box 2B, and comprises a plenum
chamber 38 in which an adjustable damper 40 is
mounted for controllinq the flow of air through the
plenum chamber 38 to the air port 30. The plenum
chamber 38 is constructed of sheet metal in the
form of an enclosed, generally rectangular duct
having substantially parallel side walls 42, 44
spaced apart by a distance corresponding with the
width of the air port 30. An end wall 46 of the
plenum chamber 38 is provided with an opening 48
substantially the size of the air port 30, and
includes lateral plates 50 formed by extensions of
3S the side walls 42, 44 of the plenum cha~ber 38, the
11 ~2~4~
lateral plates 50 extending through the air port 30
on either side thereof and into the firebox 12.
Upon installation of the plenum chamber 38 into the
wind box 28, the lateral plates 50 guide the plenum
chamber 38 into the air port 30 and serve to pro-
tect boiler tubes (not shown) from damage by moving
parts of the installed apparatus 34, as explained
hereinafter.
The,near side wall of the plenum chamber 38, as
viewed in both FIGS. 1 and 2, is shown cut away to
reveal the apparatus mounted inside the plenum
chamber. In the presently described e~bodiment of
the invention, the adjustable damper 40 comprises an
oblong, flat and generally L-shaped blade 52 made of
sheet metal and having a width siightly less than
the interior width of the plenum chamber. The
proximal end of the damper blade is attached by a
pivot 54 to the end wall of the plenum chamber
remote ~xom the opening 48, while an elongate por-
tion of the damper blade extends substantially the
length of the plenum chamber 38 from a clevis 58
affixed as by welding near the proximal end to a tip
- 60 at the dlstal end of the damper blade 52, the tip
60 being disposed in the air passage close to the
openin~ 48. The tip 60 of the damper blade 52 is
suitably made from a short length of heat resistant
metal such as stainless steel. A stiffening member
62 is welded between the distal and pxoximal ends of
the L-shaped damper blade 52. A damper actuating
mechanism comprises an air operated cylinder 64
attached to a mounting plate 66 of the plenum
chamber ~xternally of the wind box 28, and includes
an actuating rod 68, which extends through the plate
66 and connects pivotally to a connecting rod 70,
which in turn is attached by a pin to the clevis 58
12 ~1Z92~9
welded to the damper blade 52. Other motive means
such as a servomotor or a manual crank-driven worm
drive may be used instead the pneumatic cylinder
shown to change the position of the da~per blade.
Openings 72, 74 disposed below the crook of the
L-shaped damper blade in the side walls 42, 44 of the
plenum chamber receive combustion air ~nder pressure
from the wind box 28. Air from the wind box 28
flows into the openings 72, 74 and through the
plenum chamber 38 beneath the damper blade 52 and
through the opening 48 into the firebox. The posi-
tion of the damper blade 52 may be adjusted by
moving the actuating rod 68 axially toward or away
from the air port 30, thereby lowering or raising,
respectively, the damper blade 52 in the plenum
chamber to decrease or increase the flow of combus-
tion air passing through the openings 72, 74 and
into the air port 30. The damper blade may be
lowered until the tip 60 is disposed at the bottom
of or below the air port opening 48, substantially
stopping air flow through the plenum chamber 38.
Air flow through the air port 30 is subject to
attenuation by constriction of the opening 30 from
buildup of excrescent material 32, therefore,
according to the instant invention, apparatus 76
for cleaning the air port is mounted inside the
plenum chamber 38. The cleaning apparatus 76
includes a cleaning ~ead 78 pivotally mounted in a
retracted position adjacent to the opening 48, as
: 30 shown in FIG. 1, and motive means 80 mounted
externally of the wind box and extending through
the plenum for periodically operating the cleaning
head 78.
Referring still to FIGS. 1-4 and particularly
to FIG. 4, the cleaning head 78 comprises a metal
13 ~ z~9
frame affixed as by welding to a cylindrical sleeve
82 pivotally mo~nted between the side walls 42, 44
of the plenum chamber to a pivot 84 passing through
the sleeve 82, the pivot being attached to the side
walls 42, 44. The primary cleaning feature of the
cleaning head 78 is embodied in a hook-like imple-
ment 86 comprising a pair of arms138, 89 a~fixed at
proximal ends thereof to the sleeve 82, and
cleaning members 92, 93 each depending by exten-
sions 96, 97 from the corresponding arm 88, 89, the
cleaning members 92, 93 being essentially parallel
with the arms 88, 89. The cleaning members 92, 93
are spaced apart from each other in parallel rela-
tion by cross members 100-102, and the extensions
96, 97 by a trunnion 104 near their juncture with
the arms 88, 89. An actuating rod 106 is rotatably
attached to the trunnion 104 by a sleeve 108 to
which the rod 106 is welded. The cleaning head 78
is suitably constructed of heat resistant metal
such as stainless steel.
The actuating rod 106 is connected pivotally
and slidably through a mounting asse~bly 110 to an
actuating cylinder 112, preferably an air operated
cylinder, for slidably advancing the rod 106 toward
the air port 30. The cleaning head 78, is thus
adapted to rotate about the pivot 84 and pass
through the rectangular opening 48 into the air
port 30 dislodging excrescent material 32 accumu-
lated in the air port 30. As the cleaning head 78
is extended into and then withdrawn from the
opening 48, the cleaning members 92, 93 sweep the
peripheral edges of the air port 30. It will be
observed that advancing the rod 106 swings the
cleaning head 78 from the retracted position down
and forwardly from the pivot 84 into the air port
14
30~ the extended ends 114 of the cleaning members
defining a locus indicated in FIG. 2 by the dashed
line 116 wherein the cleaning members contact and
dislodge the excrescent material 32. The rod 106
is provided with an adjusting means such as turn-
buckle 118 for adjusting the length of the
actuating rod 106 upon installation of the cleaning
- apparatus 34 in the plenum chamber 38.
FIG. 1 shows the cleaning head in a retracted
position inside the plenum chamber 38 and the
adjustable damper 40 in an open position wherein
air flows through the damper into the air port,
while FIG. 2 shows a cleaning cycle in process
wherein the damper 40 is in a closed position and
the cleaning head 78 is extended into the air port
30. It is seen in FIGS. 1 and 2 that the locus of
movement of the cleaning head, as illustrated by
the dashed semicircle 120, FIG. 2, is in mutually
interfering relation with the locus of movement of
2~ the damper blade 52, shown by the dashed line 122l
FIG. 2. The upper limit of movement of the damper
blade 52, when the damper if fully open, is shown
by the dashed line 124 in FIG. 2. Accordingly,
upon initiation of a cleaning cycle, the damper
blade is lowered from the open position to the
closed position, which is outside the locus of
movement 120 of the cleaning apparatus 76, and
allows the cleaning head 78 to be actuated and
moved into the opening 48 without interference from
the damper blade 52.
FIG. 1 illustrates the c}eaning head 78 in an
at-rest or retracted position, withdrawn from ~he
air port 3~. It will be observed that the tempera-
ture inside the firebox is normally much hotter
: 35 than in the plenum chamber 3B where the cleaning
head 78 normally resides, due in part to the air
flow through the plenum chamber, and consequently
the cleaning head is protected to a degree from the
excessive temperature of the firebox except for a
brief period of use. When the damper blade is
lowered to the position shown in FIG. 2, substan-
tially no air flows throùgh the openings 72, 74
into the plenum chamber 38 and positive pressure
inside the plenum chamber with respect to the fur-
nace is reduced. Referring to FIGS. 1, 2 and 5, aturret 126 is for~ed atop and at the end ~6 of the
plenum chamber 38~ ~he cleaning head 78 moves into
the recess formed by the turret and remains there
in a retracted position between cleaning cycles,
out of the way of the damper blade 52. ~n aperture
128 in the top of the turret 126 is blocked, when
the cleaning head is retracted, by a closure 130
suitably made from a plate of sheet metal sized to
fit the aperture 128 and attached as by welding to
the cleaning head 78. Thus~ when the damper is
closed during a cleaning cycle, movement of the
cleaning head away from the retracted position
opens the aperture 128 to the wind box and air flow
through the plenum chamber to the air port 30 is
maintained.
At timed intervals, e.g. about every thirty
minutes, a cleaning cycle is initiated automa-
tically, and the cylinder 64 is actuated to lower
the damper blade 52 to the closed position as shown
in FIG. 2. The cylinder 112 is then actuatedr
swinging the cleaning head 78 into the air port 30
to the position as illustrated in FIG. 2. While the
da.~per is closed and the cleaning head is in motion,
air flows into the plenum chamber through an aper-
turet which is opened by movement of the cleaning
16
head away from its retracted position. When the
cleaning head 78 is fully engaged into the air port
30 the end 114 of the hook-shaped implement of the
cleaning head 78 rises substantially above the upper
edge of the air port while the cleaning members
sweep substantially the entire cross sectional area
of the opening. The cylinder 112 is then operated
in the reverse direction for retracting the cleaning
head 78 from the firebox back to its at-rest posi-
tion, as shown in FIG. 1. The damper is then movedfrom its closed position to essentially the same
position it occupied prior to initiation of the
cleaning cycle, or to a new position com.mensurate
with the amount of air flow required through the
plenum chamber following removal of material that
may have been blocking the air port.
Referring to FIGS. 6-8, an alternative embodi-
ment of apparatus according to the instant inven-
tion is shown. A plenum or duct 200 suitable for
installation in a wind box, not shown, for regu-
lating air flow into an air port 202 of a furnace,
includes an adjustable damper 204, cleaning appara-
tus 206 and an actuating mechanism 208. The plenum
200 is shown in each of FIGS. 6-8 with the near
side cut away to reveal the components mounted
inside the plenum. The cleaning apparatus ~06
includes a cleaning head 210, which is substan-
tially identical with the cleaning head previously
described with reference to FIGS. 1-4. kn
actuating~rod 212, pivotally and slidably mounted
through a mounting assembly 214 in the wall of the
plenum, connects the cIeaning head 210 to the
actuating mechanism 208 which is preferably an air
operated cylinder. The damper 204 is supported at
a proximal end 216 thereof in cantilever fashion to
17
allow upward or downward movement of the distal end
218 of the damper near the opening of the air port
202. The damper 20g is suitably made o~ sheet metal
having a width slightly less than the interior
width of the plenum to facilitate blocking air flow
within the plenum while allowing vertical movement
of the damper blade inside the plenum to regulate
the air flow therethrough~ The damper 204 is
affixed bs by welding at its proximal end 216 to a
coupler 220, which is pivotally and slidably
attached at its lower end to an adjustment track
222 affixed to a side wall of the plenum. ~he
coupler 220 may suitably be constructed of metal
plates so as to provide a closure of the plenum
between the proximal end 216 of the damper and the
top wall of the plenum 200. The coupler 220 is
slidably coupled to the actuating rod 212 by way of
a damper collar 224 which includes lateral pins 226
engaged in slotted apertures 228 in the sides of
- 20 the coupler 220. The damper collar 224 is slidable
axially along the actuating rod 212, but con-
strained from leftward movement, as viewed in the
drawings, by a stop 230 attached as by welding in
the ~op of the plenum 200. A first rod collar 232
affixed to the actuating rod 212 provides one seat
for a coil spring 234 through which the rod 212
passes, while a second rod collar 236, also affixed
to the rod 212, engages the damper collar 224 and
holds it snugly against the stop 230, when the
cleaning apparatus 206 is in the retracted position
as shown in FIG. 6. The end of the coil spring 234
opposite the first rod collar 232 seats against the
damper collar 224.
With the cleaning apparatus 206 in the
retracted position, damper adjustment apparatus,
~2~
18
shown here as a manually operated crank, may be
actuated to move a slidable pivot 238 of the coupler
220 left or right, as viewed in the drawings, along
the adjustmen~ track 222, respectively, to lower or
raise the distal end 218 of the damper, thereby
regulating the air flowing through the plenum 200
into thei~ir port. Although the presently described
embodiment of the invention is shown having a
manually operated damper adjustment means, it is
understood that a~tomatic means such as servomotor
controlled by a computer may be utilized to reposi-
tion the damper. In FIG. 6, the damper 204 is shown
in the fully open position, while in FIG. 7 the
damper 204 is partially closed. The stop 230
extends the entire width of the plenum as does the
coupler 220, therefore, it is seen that when the `
coupler 220 abuts the stop 230, air is blocked from
flowing over the top of the damper 204.
Referring to FIG. 8, when a cleaning cycle is
initiated by actuating the air cylinder to move the
rod 212 axially toward the air port 202, the coil
spring 234 forces the damper collar away from the
stop 230 thereby lowering the damper 204 to the
bottom of the plenum out of the way of the cleaning
head 210, which is free to move from its retracted
position,down and forward into the air port to
clean the op~ning as previously described. It is
seen that during a cleaning cycle an air passage
240 is provided between the coupler 220 and the
stop 230, and that additional air may be supplied
through an opening 242 in the top of the plenum
that is closed by the cleaning head in the
retracted position. The air cylinder is then
reve~sed to move the actuating rod 212 axially away
from the air port thereby returning the cleaning
19
head to the retracted posi~ion, whereupon ths coil
spring relaxes sufficiently to allow the damper to
return to the position it occupied prior to
initiating the cleaning cycle. Upward positive
movement of the damper 204 is provided by the
second rod collar 236 abutting the clamper collar
224 and forcing it snugly against the stop 230.
- A plurality of units of the apparatus according
to the present invention are ordinarily installed on
a single firebox for the same boiler. The dampers
may be adjusted automatically as needed by control
means, not shown, responsive to furnace instrumenta-
tion to regulate the flow of combustion air entering
the secondary air ports. The operation of the
cleaning apparatus may likewise be timed by timing
means, not shown, to be substantially completely
automatic for retracting the dampers and inserting
the cleaning heads periodically for quickly cleaning
the air ports during furnace operation, withdrawing
the cleaning heads and returning the dampers to
their previous positions.
In addition to providing improved efficiency
of boiler operation, the present invention enhances
operating safety, not only in eliminating the need
for manual cleaning and frequent adjustment of
dampers to regulate air flow to compensate for
clogged a~r ports, but also in stabilizing the char
bed which reduces the danger of hot spots and
boiler tube rupture.
While the principles of my invention have now
been made clear in the foregoing illustrative
embodiments, there will be immediately obvious to
those skilled in the art many modifications of
structure, arrangement, proportions, the elements,
material and components used in the practice of the
invention, and otherwise, which are particularly
adapted for specific environments and operating
requirements without departing from those princi-
ples. The appended claims are, therefore, intended
to cover and embrace any such modifications, wi~hin
the limits only of the true spirit and scope of the
invention.
